This invention relates to the field of disk drives and, more specifically, to components used in disk drives.
A disk drive system typically consists of one or more magnetic recording disks and control mechanisms for storing data within concentric tracks on a disk. The reading and writing of data is accomplished with a head that is used to alter the properties of the magnetic layer. The head is xe2x80x9cflownxe2x80x9d over the disk""s surface on a thin air bearing. As is well known, the actual read/write head is typically attached to a slider body having an air bearing surface that provides the necessary aerodynamic performance. Herein, the term xe2x80x9cheadxe2x80x9d may be used to denote both the head and slider body, depending on the context.
The head is positioned over a desired data track using an actuator connected by a suspension arm to the head. The actuator moves the head in a radial direction to the desired track. A spindle motor rotates the disk to position the head at a particular location along the desired track. Spindle motor assemblies typically include a rotatable spindle hub that is carried by a fixed spindle shaft securely mounted to the disk drive""s housing. One or more disks are positioned on the spindle hub with spacers provided between adjacent disks to allow for head to be positioned between the disks. The disks are clamped on the spindle hub with a disk clamp.
Head flight results from the compressed air between the head (air bearing) and the rotating disk. This develops a boundary layer of air carried by the rotating disk, above its surface, that lifts the head away from the disk in opposition to a loading force from the suspension arm. Therefore, it is important to maintain precise clearance between the head and the disk""s surface. As such, the flatness of a disk may affect the flying characteristics of the head.
Drive manufacturers specify a flatness required for disks to operate within their system. Disks are typically manufactured to meet such disk flatness specifications. In general, the flatter the disk, the better its performance within a disk drive. The flatness of a disk may be defined in terms of the difference between the highest and the lowest point on a disk, referred to as total indicated run-out (TIR). Many disk drives currently require TIR to be less than 15 microns for a disk 0.8 millimeters (mm) thick. A warped or bent (i.e., concave or convex) disk may vary the spacing between the head and the disk at different positions and, thereby, cause undesirable disk contact with the flying head during operation of the drive. Successive head contact with the disk surface wears through protective coatings on the disk that may lead to corrosion of the magnetic layer and, thus, corruption of data stored therein. Moreover, severe head contact with the disk may cause the drive to crash and possibly render the drive non-functional.
Typically, prior drive systems rely on the use of a disk that is manufactured to be substantially flat to maintain precise clearance between the head and the disk""s surface. The drive""s spindle assembly uses a disk clamping mechanism that provides a uniform clamping force along its area of contact with the disk to avoid distortion of the disk. One problem such a drive system is that the disk clamp may be limited only to use with a substantially flat disk. The disk drive may not be able to utilize disks that are manufactured outside a TIR specification. Such a disk drive system may not be desirable because of the higher cost of using a substantially flat disk in comparison to the use of a warped disk that may be less expensive.
The present invention pertains to a method and apparatus for compensating disk warpage. In one embodiment, the apparatus may include a disk and a plurality of spacers coupled to the disk to provide unbalanced moments on the disk.
Additional features and advantages of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.